Method of dry cleaning and rendering fabrics water repellent



United States Patent METHOD OF DRY CLEANING AND PmENDERING FABRICS WATERREPELLENT Leo J. Novak, Dayton, Ohio, assignor to The CommonwealthEngineering Company of Ohio, Dayton, Ohio, a corporation of Ohio NoDrawing. Application June 18, 1953 Serial No. 362,659

1 Claim. (Cl. 11'7-66) This invention relates to dry cleaning and moreparticularly to compositions and methods for simultaneously dry cleaningfibrous materials such as articles of clothing and the like andimparting water-repellency thereto.

There are a number of methods now employed for waterproofing fabrics.For example, raincoats are usually waterproofed by impregnating thecloth with a solution of an oil-soluble soap such as aluminum stearate.Different types of waxes are also used. Such treatments do impart ameasure of water-resistance to the fabric but, as is known, even thoughthe waxes and soaps may be insoluble in water or the common dry cleaningsolvents, the water-resistant effect does not last for the life of. thegarment because the adhesion of these substances to the fibers of thefabric is not particularly strong and the coating tends to rub offduring use.

Synthetic resins have also been proposed and used, but have thedisadvantage that, in order to compensate for the antipathy between thehydrophobic resins and the hydrophilic fibers of the fabric, thefinishers tend to load the fabric with the resin, thereby rendering thefabric so stiff and boardy that it becomes necessary to subject it toworking on flexers which break up the continuity of the resin coating toleave the resin on the fabric in the form of discrete particles. Suchparticles tend to peel off in use and, also, the discrete condition ofthe resin may lead to swelling and distortion of some of the fibers onexposure of the fabric to moisture.

Methods involving chemical alteration of the fibers of the fabric, as bytreating the fabric with formaldehyde in the presence of an acid oracid-yielding catalyst, have been proposed for controlling the swellingof hydrophilic fibers in water, which is, in effect, to impartwaterresistance to the fabric. Despite the extensive research which hasbeen carried out with a view to perfecting these methods, including theuse of softening agents conjointly with the formaldehyde or the like, itis known that no commercial method has been developed which does notresult in some embrittlement of the fibers and fabric.

it is a fact that, regardless of the composition and method used forrendering the fabric water-repellent, the effects of the treatment donot persist for the life of the garment for one reason or another, and,in practice, the water-repellent effect has to be renewed periodically.For instance, it is a common occurrence for those who prefer raincoatsmade of fabric (as opposed to resin film or sheet material which doesnot breathe nor possess good draping quality) to instruct thedry-cleaner to water-proof the garment before returning it.

Since, invariably, it is necessary to renew the waterrepelling orwater-resisting effects by periodically treating the fabric or garmentwith a water-repellent, the primary object of this invention is toprovide a means Q 'ice and method for rendering fabrics water-resistantor waterrepellent during dry cleaning thereof without requiring specialhandling of the fabric or after-treatments performed on the cleaned anddried fabric.

A further object is to impregnate fabrics, for example cotton, wool andregenerated cellulose fabrics, with a Water-repelling substance whichadheres tenaciously to the fabric, does not tend to peel or rub off, andprevents wetting or spotting of the fabric by water in use.

These and other objects are achieved by the present invention inaccordance with which, during dry cleaning thereof, fabrics to berendered water-resistant are impregnated or coated with certain fattyacid esters of a dextran or of a partial dextran conversion productcontaining, initially, some hydrophobic substitutent groups and somefree hydroxyl groups dissolved or dispersed in the dry cleaning solventor solvent mixture.

The dextrants are inherently hydrophilic high molec ular weight,branched polysaccharides comprising anhydroglucopyranosidic units joinedby molecular structural repeating alpha-1,6 and non-alpha--l,6 linkages,,at least 50% of the linkages being, apparently, alphal,6 linkages. Theproperties of the dextrans, including the extent of branching (numberand distribution of side chains or groups), the molecular weight, themolecular structural repeating alpha-1,6 to non-alpha-1,6 linkagesratios, and the sensitivity to water vary.

It is found that esters of the dextrans with saturated fatty acids offrom 8 to 18 carbon atoms and having a BS. (degree of substitution ornumber of fatty acid radicals per anhydroglucopyranosidic unit of thedextran) from 2.0 to 3.0 are water-repellent substances which have anaffinity for hydrophilic fibrous materials and are or garment isimpregnated with, or carries a protective,

water-repellent film or coating of, the ester which remains adhered tothe fabric until it is again dry-cleaned, when the Water-repellentfinish may be renewed.

The higher saturated fatty acid radicals may be introduced into thedextran molecule by any appropriate method. Thus, the dextran,preferably in the form of a freefiowing powder, may be reacted with anesterifying derivative of the fatty acid, and preferably a halide suchas the chloride thereof, in the presence of an acid acceptor or bindingagent such as an organic base, as for instance a heterocyclic tertiaryamine of the type of quinoline, pyridine, N-methyl morpholine, etc., andin the presence of a substance in which the reaction product is at leastpartially solvated, that is dissolved or swollen, as it is formed duringthe reaction. This results in the reaction mass being maintained in ahighly swollen or dissolved state and thus insures substantiallyuniform, homogeneous reaction between the dextran and the esterifyingagent.

Substances which dissolve or swell the ester as it is formed are, forexample, xylene, toluene, dioxane, etc.

In general, the reactionmay be carried out at temperatures between C.and C. for time periods varying inversely with the temperature between ahalf hour and three hours. The ester may be recovered from the crudereaction mixture by washing the latter with water to remove thehydrochloride of the organic base, removing the aqueous layer, adding asolvent for the ester to ether and dichloroisopropyl ether.

the residual mass, precipitating the solution into a nonsolvent for theester, such as a lower aliphatic alcohol, and filtering to obtain theester.

Also the introduction of the higher fatty acid radicals into the dextranmolecule may be effected by reacting the dextran with the selected acidin the presence of an impeller which may be the anhydride of amonohalogenated monobasic organic acid, e.g., monochloro aceticanhydride, and an esterification catalyst such as magnesium perchlorateat temperatures at which the reaction mixture remains in the liquidstate, in general in the range between 50 C. and 100 C. and for a timevarying inversely with the temperature between one-half hour and twohours. The ester may be isolated from the crude reaction massbycoolingthe mass, dissolving it in a solvent therefor, precipitating it into anon-solvent for the ester, and filtering the ester.

The higher fatty acids which may be used as esterification agent, in thefree acid form or in the form of their chlorides, are those saturatedacids containing from 8 to 18 carbon atoms and including caprylic,pelargonic, palmitic, margaric,'and stearic acids, and the correspondingchlorides. Two or more of the substantially pure acids, or chloridesthereof, may be used, resulting in the production of mixed dextranesters. Or commercial acids, which comprise mixtures, may be used. Forexample, commercial or technical grade stearic acid, which comprises amixture of stearic and palmitic acids, yields dextranstearate-palmitate.

As has been mentioned hereinabove, the esters to be used aswater-repellents in the dry cleaning solvents are those having a D8. offrom at least 2.0 up to 3.0. Other conditions, such as the reaction timeand temperature, being appropriately controlled, such esters may beobtained by using the fatty acid or itsrchlorides in amounts varyingbetween about 2 and 10 parts thereof by weight per part of dextran.These highly substituted dextran esters, and more particularly thosederived from the saturated acids of longer chain'length, i.e., thosecontaining between 14 and 18 carbon atoms, have a waxy consistency and,in addition to rendering the fabric waterresistant, also give it a soft,pleasing hand or feel.

The production of these dextran esters is exemplified in detail, andclaimed in the pending-application of L. I. Novak et al., Serial No.371,743, filed April 28, 1953, and now abandoned.

The dextran esters described herein are soluble in the solvents commonlyused in dry cleaning, such as Stoddards solvent, gasoline and cleanersnaphtha. They are also soluble in the nonfiammable chlorinated compoundswhich are rapidly replacing flammable solvents like naphtha in the drycleaning trade and including carbon tetrachloride, ethylene andpropylene dischloride, trichlorethane, trichloroethylene,perchlorethylene, dichloroethyl The esters are also soluble in mixturesof these solvents with each other and with neutral soaps such as themixtures oftenused in commercial large-scale dry cleaningestablishments.

The solutions may be prepared and marketed as such for home orlarge-scale commercial use or just prior to use they may be prepared byadding the ester to the solvents. For example, in the commercialcleaning houses the ester may be added to clarified, used solvent as hisrecirculated to the tumbler or washing machine. -The concentration ofthe dextran ester in the solution may vary depending on the type. offabric, garment or fibrous aritcle treated, larger amounts beinggenerally desirable for heavier fabrics.

As a general rule solutions containing from 1% to 20% by weight will befound satisfactory, the conditions of the treatment being controlled sothat the amount of dextran ester deposited on the fabric is between 2%and 5% on the fabric weight.

7 The 'fabric or the like to be dry-cleaned may be introduced directlyinto the ester solution. When the dry cleaning procedure involves adual-step method in which the fabric or garment is washed in the solventand then rinsed in fresh solvent or in clarified used solvent, thedextran ester may be present in both baths but is preferably present inthe rinsing bath, only. For instance, in one commercial method of drycleaning fabrics according to the invention, a batch of 20 lbs. ofsoiled garments is placed in the Washing machine of conventional typeand containing the usual quantity of solvent, such as carbontetrachloride. The clothing or the like is then agitated in the solventfor approximately 10 minutes to remove loose dirt. The solvent is thenre moved and clarified bypassage through a suitable filter, bycentrifuging, or by allowing the dirt to settle and decanting off theclarified supernatant.

The purpose of removing and clarifying the solvent at this point is toprevent loading thereof by dirt, grease, etc. removed from the garments.Before the clarified solvent is returned to the machine for furtherwashing of the garments, etc. it is fortified by the addition of asulficient amount of water-resistant dextran ester, for example adextran palmitate containing, per anhydroglucopyranosidic unit, anaverage of about 2.9 palmitoyl radicals,

or a dextran stearate containing, per anhydroglucopyram osidic unit, anaverage of;2.9 stearoyl radicals, to provide a cleaning andwater-repelling solution of the required concentration.

The solution of the ester is entered into the tumbling machine andagitated with the clothing forthe predetermined length of time. Thetreated goods is then removed from the machine and dried in the usualway.

There is thus obtained a cleaned article carrying a renewablewater-repellent finish. The articles being cleaned may be forwarded fromone machine or compartment to another and treated at each stage with thedry cleaning solvent, and at least at the final stage with a compositionconsisting of a solution of the dextran ester in the solvent or mixedsolvents.

Instead of esters of dextran there may be used esters of dextranconversion products containing, per anhydroglucopyranosidic unit, anaverage of at least 2.0 of the radicals derived from the saturatedaliphatic acids, of from 8 to 18 carbon atoms and, in addition to thoseradicals, an average of about 1.0 hydrophobic substituent such as alkylradicals of 1-5 carbons or aralkyl radicals of 7-10 carbons, total.

Preferably, the esterified dextran product does not contain more than anaverage of 1.0 free hydroxyl group orradical of hydrophilic characterper anhydroglucopyranosidic unit and has little, if any, waterattracting powen In-the specifically preferred embodiment, the

water-repellants contain, per anhydroglucopyranosidic' unit, between 2.5and 3.0 substituent groups at least 2.0 of which are derived from thesaturated fatty acids.

The dextrans to be esterified may be obtained in various ways. Forexample, they may be produced microbiologically, by inoculating anutrient medium containing sucrose, particular nitrogeneous compoundsand certain inorganic salts, with an appropriate microorganism, such asthose of the Leuconostoc mesenteroides and L. dextranicum types, andincubating the culture at the temperature most favorable to the growthof the particular microorganism.

In one method of obtaining a dextran to be esterified to produce thewater-repellents for incorporation in the dry cleaning composition ofthe invention, there is first prepared an aqueous nutrient medium whichmay have the following composition:

Percent by weight This medium is adjusted to a pH of between about 6.5and about 7.5, preferably 7.2, and then sterilized. The material iscooled to room temperature and inoculated with a culture of thedextran-producing microorganism, for instance, Leuconosmc mesenteroidesB-S 12 (Northern Regional Research Laboratory classification) andincubated at 20 to 30 C. (optimum 25 C.) until a maximum yield ofdextran has been attained; normally a period of between 12 and 48 hourswill be satisfactory for this procedure. The fermented product containsapproximately 80-85% of water and is a thick turbid liquid.

Upon completion of the fermentation, which process renders the materialsomewhat acid, that is, to a pH of 3.5-5.5 (average 4.2), calciumchloride is added to the ferment to bring the pH thereof to about 7.0 to8.0. This aids in the precipitation of phosphates. Thereafter, acetoneor alcohol, which may be a water-miscible ali phatic, such as methyl,ethyl or isopropyl, is added in sufiicient quantity to precipitate thedextran and this brings down, with the dextran, occluded and adsorbedbacteria, and nitrogenous and inorganic elements. To occasion completeprecipitation of the dextran it may be desirable to allow the mix tostand for a relatively long period, such as about 6 hours. Theprecipitated dextran may be dried in any suitable manner, for example bydrum drying. Thereafter, it may be reduced to a powdered condition, ifdesired.

A purer dextran may be obtained by adding an aliphatic alcohol to thefermented culture at a pH between about 2.5 and 4.5. The precipitatethus obtained may be further purified by again precipitating it with thealcohol. Several precipitations may be performed.

The dextran thus produced is a so-called native dextran having a highmolecular weight and being, in the particular case, soluble in water atordinary temperatures.

The higher saturated fatty acid radicals may be introduced into themolecule of high molecular weight dextrans such as the native dextrandescribed above, or other dextrans of equivalent or similar highmolecular weight, or lower molecular weight dextrans may be used asstarting material for production of the water-resistant esterscontaining chemically bound radicals derived from the saturated fattyacids.

Lower molecular weight dextrans may be obtained directly or byhydrolysis, in any suitable way, as by acid or enzymatically, of highermolecular weight dextrans. The hydrolyzed material may be fractionated,if desired, and the dextran may be a so-called clinical" dextran of thetype useful as a blood plasma extender.

In general, the dextran may have a molecular weight between 5,000 and150x10 as determined by light scattering measurements.

The dextran may be obtained by inoculating a culture medium of the typedescribed with microorganisms other than that mentioned above. Thus, itmay be a water-soluble dextran obtained by the use of the microorganismsbearing the following NRRL classifications; Leuconostoc mesenteroidesB-l19, B1l46, Bll90, or a water-insoluble or substantiallywater-insoluble dextran obtained by the use of Leuconostoc mesenteroidesB-742, B-1l91, B-1196, B4208, 13-1216, 13-1120, B-ll44, B-523,Streptobacterium dextranicum B-1254 and Betabactcrizmz vermiforme13-1139.

The dextran is not limited to one prepared under any particular set ofconditions, including the microorganism used. It may be producedenzymatically, in the substantial absence of bacteria, by cultivating anappropriate microorganism, for example, Leuconostoc mesenteroides B-512to obtain a dextran-producing enzyme, separating the enzyme from themedium in which it is produced, and introducing the enzyme into a mediumin which dextran is produced by the action of the enzyme. Also, thedextran may be obtained by bacterial conversion of 1,4 linkages ofdextrin to 1,6 linkages of dextran. The dextran may be insoluble inwater under ordinary conditions but soluble in aqueous alkali solution.

In the presently preferred embodiment of the invention, thewater-resistant fatty acid esters are derived from substantially purenative unhydrolyzed microbiologically produced dextrans precipitatedfrom culture media of the types described herein, or from dextrans ofequivalent high molecular weight.

The higher saturated fatty acid esters of the dextrans are stronglywater-repellent. For instance, it has been observed that if a film ofdextran palmitate 0r dextran stearate containing, peranhydroglucopyranosidic unit, an average of 2.9 palrnitoyl or stearoylgroups is deposited on the hands during handling of the solutionsthereof, the film is not removed by repeated washing or scrubbing withsoap and water.

The strong resistance to water coupled with the effective substantivitywhich these esters exhibit for fibers of hydroxylated materials rendersthem ideally adapted to use as renewable water-repellents to be appliedto garments and other articles in the course of dry cleaning the same.The esters are applied to the garments or the like while they are beingcleaned, and no after-treatment or special handling is required.

No special precautions or use of elevated or baking temperatures arerequired such as must be performed when the water-repellent is asynthetic resin, nor are the fabrics subjected to harsh conditionsleading to embrittlement or loss of strength. The dextran esters protectthe fibers, tend to increase their strength and resistance to abrasion,and to improve the suppleness and drapability of the fabrics, so that,in addition to rendering the fabrics water-resistant or water-repellentthe esters of the dextran or dextran conversion products exertbeneficial effects on the quality of fabrics drycleaned in accordancewith this invention which, therefore, provides a means and method fortreating fabrics by means of which, in essentially a single-stepprocedure, the fabric is dry-cleaned, conditioned, and rendered stronglywater-resistant. The esters do not detract from the effectiveness of thedry cleaning compounds as scouring and degreasing agents for fabrics.The dispersions or solutions of the esters in the dry cleaning solventsare stable. The term solution as used herein includes colloidalsolutions or dispersions.

It will be understood that while there have been described certainspecific embodiments of this invention, it is not intended thereby tolimit or circumscribe it by the details given, in view of the fact thatthis invention is susceptible of various modifications and changes whichcome within the scope of this disclosure and of the appended claim.

I claim:

In amethod of dry cleaning fabrics comprising washing the fabric in asolution containing volatilizable organic solvents and then separatingthe solution from the fabric and drying the fabric, the improvementwhich consists in simultaneously cleaning and waterproofing the fabricby washing the same in a dry cleaning solvent containing from 1% to 20%by weight of a saturated fatty acid ester of dextran, said saturatedfatty acid containing from 14 to 18 carbon atoms in the molecule, andthe dextran having a molecular weight between 5,000 and x10 and producedby the reaction of sucrose with a dextran-producing strain ofLeuconoszic mesenteroides, and separating the washed fabric from saidcleaning solvent leaving a residue of said dextran fatty acid ester offrom 2% to 5% based upon the weight of the fabric thus treated, said drycleaning solvent being selected from the group consisting of carbontetrachloride, ethylene dichloride, trichlorethylene andperchlorethylene and mixtures thereof.

(References on following page) References Cited in th file of thispatent UNITED STATES PATENTS Lejeune et a1 Oct. 29, 1935 Bucy Nov. 28,1939 Stzihly 61; 3 1. .2 Jan. 23, 194 1 Thackston et 'al. Mar. 21, 1944Maxwell Sept. 26, 1944 Walde Oct. 16, 1945

